1. Technical Field
Embodiments of this disclosure relate to a cooling device to cool a recording material while sandwiching and conveying the recording material and an image forming apparatus incorporating the cooling device.
2. Description of the Related Art
Image forming apparatuses are used as, for example, copiers, printers, facsimile machines, and multi-functional devices having at least one of the foregoing capabilities. As one type of image forming apparatus, electrophotographic image forming apparatuses are known. Electrophotographic image forming apparatuses have a fixing device to fuse toner under heat and fix a toner image on a recording material (e.g., a sheet of paper). In such an electrophotographic image forming apparatus, recording materials having toner images fixed thereon may be stacked on, e.g., an output tray. In such a case, the recording materials having toner images are stacked one on another on the output tray in heated state. As a result, toner is softened by heat retained in the stacked recording materials, and pressure due to the weight of the stacked recording materials may cause the recording materials to adhere to each other with softened toner. If the recording materials adhering to each other are forcefully separated, the fixed toner images might be damaged. Such an adhering state of the stacked recording materials is referred to as blocking.
To suppress blocking, a cooling device may be used to cool a recording material after a toner image is fixed on the recording material under heat. To cool a recording material, different types of device (hereinafter, cooling device) are proposed including a cooling member with a cooling surface to directly or indirectly contact the recording material and absorb heat of the recording material for cooling.
As a way of bringing the cooling surface into contact with a cooling target, for example, the following device is proposed. For example, in a cooling device, a cooling surface of a cooling member directly contacts a recording material to cool the recording material (hereinafter, direct contact system). For the direct-contact-type cooling member, for example, a recording material slides over a cooling surface of the cooling member, or a cooling surface (outer surface) of the cooling member having a roller shape contacts a recording material and is moved in response to conveyance (movement) of the recording material. Alternatively, in a cooling device, a cooling surface of a cooling member contacts not directly but indirectly with a recording material via an endlessly movable belt member (hereinafter, endless belt) to cool the recording material (hereinafter, indirect contact system). Recently, in any of the direct contact system and the indirect contact system, to obtain a good balance between cooling efficiency and space saving, cooling devices have increasingly employed a configuration in which a recording material or an endless belt sides over a flat or curved cooling surface, which is likely to obtain a wider area of the cooling surface.
In addition, for heat absorption and radiation, for example, the following systems are proposed. For example, for an air cooling system, a blower blows air against a radiation member, such as a cooling fin connected directly or indirectly (via a heat transmitter, such as heat pipe) to a cooling member, to radiate heat absorbed by a cooling surface of a cooling member. Alternatively, for a liquid cooling system, a cooling member includes a channel for cooling liquid. A radiation member, such as a radiator, disposed outside the cooling member and a liquid feed unit, such as a pump, are connected to the channel of the cooling member via tube channels, such as pipes. When the cooling liquid is circulated by the liquid feed unit, a cooling surface of the cooling member absorbs heat of the cooling liquid and a radiation member radiates heat to the outside. Furthermore, in another system, a heat transmitter is directly disposed in a cooling member. A Peltier device is connected to the cooling member to radiate heat, utilizing a Peltier effect that, when electric current flows through a joint portion between two different types of metal, heat transfers from one metal to the other metal.
For example, JP-2012-173640-A proposes a cooling device to cool a recording material while sandwiching and conveying the recording material by two sandwiching units having endless belts. The cooling device employs a liquid cooling system and an indirect contact system to slide an endless belt over a cooling surface of a cooling member. An inner circumferential surface of the endless belt of one of the sandwiching units (at a side facing toner fixed on a recording material) slides over the cooling surface of the cooling member. For the cooling device, a base material of the cooling member is post processed to form an internal channel for circulating the cooling liquid. To improve drainage of condensation occurring on surfaces of the cooling member, post-processing, such as surface processing for water repellency, is conducted on the cooling surface or other surfaces of the cooling member.